Conventionally, a microphone unit is provided in sound communication devices, such as mobile phones and transceivers, information processing systems, such as voice authentication systems, that utilize a technology for analyzing input voice, sound recording devices and the like. At the time of conversation by a mobile phone or the like, voice recognition and voice recording, it is preferable to pick up only a target voice (user's voice). Thus, there is an ongoing development of a microphone unit which accurately extracts a target voice and removes noise (background sounds, etc.) other than the target voice.
To provide a microphone unit with directivity can be cited as a technology for picking up only a target voice by removing noise in a use environment where noise is present. As an example of microphone units with directivity, a microphone unit which is formed such that a sound pressure is applied to both surfaces of a diaphragm and converts an input sound into an electric signal utilizing vibration of the diaphragm based on a sound pressure difference has been conventionally known (see, for example, patent literature 1).